Method of aerial mapping



Jana 12, 1954 J. E. HENRY METHOD oF AERIAL MAPPING Filed March 2, 1951 3Sheets-Sheet l R. m n W.

Jan. 12, 1954 J, E HENRY 2,665,481

METHOD OF AERIAL MAPPING Filed March 2, 1951 3 Sheets-Sheet 2 IINVENTOR. J/Wf E /75/1/ J/ Jan. 12, 1954 J, E, HENRY METHOD oF AERIALMAPPING 3 Sheets-Sheet 5 Filed March 2, 1951 atenteci `an. 1K2, 1954UNITED STATES PATENT OFFICE (Granted under Title 35, U. S. Code (1952),

sec. 266) 5 Claims.

The invention described herein may be manuiactured and used by or forthe Government for governmental purposes without payment to me of anyroyalty thereon.

This invention relates to a method of mapping terrain photographicallyfrom an aircraft. Heretofore it has been a considerable problem to ny amapping course so that the pilot nying the adjacent course to make astrip map of the terrain adjacent to that covered in the nrst coursewould be able to interlock satisfactorily the second mapping strip withthe nrst mapping strip. The nrst mapping strip was never instantaneouslyavailable as a guide for the second night or subsequent nights.Development and printing of the various strips necessitated grounding ofthe airplane between each strip ilown in order to obtain a check forside-lap purposes.

The recent invention of the instantaneous developing and printing cameraby Edwin C. Land is the basis of the present improvement in aerial stripmapping. The Land camera, which is now well known, is based on Patents2,435,717, 2,435,718 and 2,435,720. Brieny stated, the new methodcomprises ying a strip course while photographing a terrain directlyunderneath with a conventional mapping camera and at the same timephotographing the terrain on one side of the strip with a second camera,a Land camera, the field of which extends into unknown territory. Thephotograph made by the second camera is used for navigating the aircraftalong the next night line. The navigation photography, which is atsubstantially a right angle to the strip being nown and mapped, isperformed with one of the two Land cameras with which the aircraft ispreferably provided. When the airplane reaches the end of the stripintended to be mapped it will execute a hairpin turn whereby it willthen be in a position to ny the adjacent strip in the oppositedirection. The time which is used in making the straight night and tomake the turn is employed by the photographer to develop the printsalmost automatically one by one in the Land camera and from them to takeprints one by one which bear a line indicating the course to be flown.This line is obtained by means of a wire stretched in the focal plane ofthe Land cameras so that the views taken by them are dividedlongitudinally into halves by the resulting line. While, of course,there is no line over the actual terrain which is to be flown on thesecond course, still the location of the imaginary line over the actualterrain can be inferred from the landmarks which the photographed linetraverses. The short time neces" sary for the development of the Landprint enables an airplane to map a large amount of previously unmappedterrain by nying a parallel grid course over it without the necessity ofmaking any landings for the purposes oi developing or matching nlm. Thelast print developed on the turn is the nrst one utilized by the pilotfor determining the location of this next straight line of night, andthe remaining ones are consulted in the order which is the reverse oithat in which they were made.

One object of the invention is therefore to inap terrain without thenecessity of having any preliminary large scale maps of the areas whichhave heretofore been necessary for plotting the night lines to be flownand for navigating the night lines while flying the mosaic.

Another object is to render it possible to map hostile territory ofwhich no maps are available, without the many re-nights which have beenheretofore required and which is expensive in both time, money andpossibly life.

Another object is to provide a mapping method in which night lines ofany length may be nown and to obtain photography of the area in achecker-board or mosaic pattern with a standard amount of side-lap andoverlap.

Another object is to provide a more rapid method of mapping than hasheretofore been available, especially when the time requirement forputting the strip maps together is conn sidered.

vAnother object is to provide a method, flying a map mosaic the baseline of which need be only the location and direction of the firstnight. if a plane drifts ofi= course, i. e., out of parallelism with thenrst night, this night line can be recognized immediately as being outof parallelism and may be re-nown before flying the next night line orstrip.

Referring now to the drawings:

Fig. l is a diagram showing a fragment a vertical cross-section of anairplane fuselage with cameras mounted therein, the angular relationsbetween the terrain and the cameras being shown by lines directed to abase line which represents the ground;

Fig. 2 is a view corresponding to Fig. 1 in which the relations betweenthe photography in one strip or night is correlated with the photographymade by the same or different airplane when it is mapping adjacentstrips;

Fig. 3 is a plan view diagrammatically presented, of an airplane whichis ying a series of parallel flight lines over terrain to be mapped, thedashed circles indicating the range of photographs which are made fromthe airplane at intervals according to the new method;

Fig. 4 is a perspective view of a simple type of camera mount which isused to determine adjustably the angular positions which are to beoccupied by the Land cameras during the mapping flights. This mount perse is not regarded as invention; and

Fig. 5 is a schematic showing the. making of the finished map mosaic,the Land camera photographs being shown as small squares superposed onover-lapping and side-lapping according to the Example 1 which is now tobe described, be able to photograph the terrain ineluded within an angleof 72", the origin of which is the focal plane of the camera i I.

Also mounted within the fuselage I il are a pair of Land cameras Hic;and Ilib each attached to a mount which is shown in Fig. 4 and indicatedgenerally by l5, the mounts in Fig. 1 being respectively Via and I5b.The mounts rest upon blocks or supports which are designated in Fig. 1respectively as ita and IIib. These blocks have a top surface which isparallel to the longitudinal axis of the fuselage. When a standard 30%side-lap between strips is desired on the negatives which are to befurnished by the mapping camera, the cameras Illa and Idb` are directedthrough windows or openings (not shown) in the fuselage at an anglewhich is 46 and 24 from the Vertical as measured from the line I3a tothe center of the adjoining night line. ff a different amount of sidelapping is desired, photographers will know how to alter the angleaccordingly on the Land navigation cameras. For 6" focal length mappingcameras of 9" x 9 format, the Land or navigation cameras Ilia and Ilibshould be installed with a 43-36 depression angle for 30% side-lap. Thedepression angle varies with the focal length, format sizes and percentside-lap so that a plus or minus 5 variation is permissible toaccommodate various kinds of cameras.

It is possible to dispense with the wire which has been mentioned asbeing positioned across the focal plane of the Land camera, since aglass or Plexiglas plate with an etched centerline may be placed overthe print after it is removed from the Land camera, or the print itselfmay be folded lengthwise to create a center line. However, itfacilitates the operation if such a line be present. Since lines havepreviously been placed on negatives by means of wires to facilitatelocations in aerial photography as for example, Patent No. 2,358,777, ithas been deemed unnecessary to show the means of obtaining such a lineon the negative.

The angle 0 shown on Fig. 1 is not a camera angle, but is an angle whichsubtends the distance between successive iiight strips. Line i319indicates the center of the next flight strip. Line i3 indicates thecenter of the adjoining flight strip on the right. Line I3a thereforeindicates the vertical line which bisects the flight strip being flown.Point M represents they junction of lil d line I3b with the base line I2and point N is the junction of line I3 with the base line.

Each Land camera ida and Iib is directed respectively to the junctionpoint M or N, whichever is on its appropriate side. It has been foundthat to intersect the points M and N, the Land cameras must be sightedat an angle e524 from the vertical. The lines bounding the angles 0 are43-36 from the horizontal line C which is substantially tangent to thefuselage of the airplane It, assuming the fuselage to be scmicircular.The angle between the line i3d and each boundary of the angle 0 is46-24- The lines D and E which bisect the field of view of the Landcamerasv Ida and ifib, respectively, must intersect the points M and N,respectively, with the maximum obtainable exactness. The lines D and Eare represented on the photographs taken by the Land cameras by thelines produced by the wire spoken of previously as having been stretchedlongitudinally in the focal plane of these cameras.

Referring now to Fig. 4, the mount i5 comprises a baseboard il and anangular adjustable board i8 which are pivot-cd together at one edge ofeach board by a pivot i9. Thebasebcard il is provided with asemicircular slot 2f! through which extends a bolt 2l which is anchoredinto one of the blocks iba or lh. The bolt 2i is provided with a wingnut 22 whereby a position of the board Il can be fixed on the block lBaor ib. An opening 23 is provided for a pivoting bolt (not shown) whichextends upward from the block Hic or lh near the fuselage wall. Themount is consequently able to pivot through an angle which may begoverned by the length of the slot 2S, which is a segment of the circlewhich would be generated in the board 28 by the bolt 2| upon rotation ofthe board, assuming that the board furnished no resistance to the bolt.Drift of the aircraft can be compensated. for by altering the angularposition of the mount about the pivot 23 and clamping it by the wing nut22 into the appropriate position. Between the boards I'I and I3 there isan arcuate strut 24 in which there is a slotv 25 through whichV projectsav bolt 26, which bolt is attached to one edge pf the board I8. Therelative angular positions of the two boards may then be adjustablydetermined by locking the board IS to the strut 2d by means of a wingnut 2l on the bolt 25 which extends through the slot 25. The strut ispivoted on the baseboard il by a pivot 28 which enters the edge thereof.

Referring now to Fig. 2, the three fuselage sections Iil represented inthis figure are correlated with the positions of the airplane '39represented in Fig. 3. At the right-handV side of Fig. 2 the airplane iscoming toward the observer. Tfn the middle of the three fuselages, theairplane is going away from the observer and on the lefthand side of theairplane is again approaching him.

The points N and M on Fig. 2v are the same as those appearing on Fig. 1on the base line I2, likewise perpendicular lines I3, i3d and I are alsothose which intersect the base line I 2 on Fig. 1. On the base line I2in Fig. 2 the amount of side-lap, which has been standardized at 30% isindicated, this being the amount of side-lap of the view taken by themapping camerav iI as aresult of its 72 angular coverage. Obviouslythese angles can be modified without departing from the spirit of theinvention.

In Fig. 2 will also be seen how the left-hand and camera in each casecenters its field of View the theoretical line which would extend back ro the paper from the point where the lines i3d. and ib join the baseline I2. These -,iaginary lines, which are fully shown in Fig. 3onstitute the night path to be followed by the airplane in making itsseries of parallel progressive courses from right to left. The turns areomitted in 2 but appear in Fig. 3. The pilot therefore, since hedevelops the Land camera views obtained while he is following onestraight -night path, is in almost instantaneous possession of a pictureof the next night path that he must follow and which is available to himas a result of his developing the image while irr flight indicated inFig. 3.

While this method may he carried out by using a continuous strip camerasuch as the .Sonne camera as the camera Il, in Fig. 3 the large dashedcircles 3U, 3i and 32 indicate exposures made in different night stripsor courses by an intermittent exposure mapping camera Il. Experience hasdemonstrated that most military aviation maps can be satisfactorilyconstructed by the use of exposures made when the airplane has reachedthe approximate positions in the flight path in which it is 'shown inFig. 3. This gure also indicates that one Land camera is also operatedat the same time that the mapping il exposes iilm. 33 indicates theareas photographed by the Land camera. The Land camera need be exposedabout once in every ten miles night to make a satisfactory map. There isno set distance between the straight flight paths of the airplane, sincesuch distance will vary according to the elevation iiown, but theangular relations will remain generally the same. However, the higherthe point from which the photographs are made, the greater the amount ofterrain photographed at one time and the further apart the straightflight courses will be. The straight flight courses may be quite long,say one hundred miles or more.

In the interpretation of Figs. 1 and 2 it should 'be borne in mind thatthe aircraft actually flies at such a great height that it ispractically a point source of observation, Angles referred to points Aand E on this figure, when the airplane is at high altitudes, becomesubstantially coincident. Therefore the Land cameras and the mappingcamera l l both take photographs from substantially the same point.

ln Fig. 5, two strips or courses, 34 and 35 respectively, are beingflown by an airplane 29. Tie center line of course 34, which theairplane 2Q follows, is 35. The oppositely flown center line of course35 is 37. The center line of the course which will next be flown is 38.The small squares 35i indicate Views made by the Land cameras, some madefrom the right and some from the left side of the airplane.

l'n Fig. 5 the views `4| made by the mapping camera l i extend from onefull dotted horizontal line 43 to the other. The vertical dotted line 42indicates the left boundary of the mapping camera views lli It isapparent therefore that there is a side-lap between the strips 34 and 35which is shown by dotted lines 43 and also indicated by legend at thetop of the figure. The sidelap is 30% of the width of a photograph 4|.

It is evident also that overlap, indicated by a bracket and 114 on strip34, exists and is desired. The preferred amount is 60% of the length ofthe photograph 4 I.

Fig. 5 therefore gives schematically the order which all of thephotographs 4! are arranged s Gl for the purpose of mapping the terrain.While the use of an intermittent exposure mapping camera has beensupposed the Sonne type of continuous exposure camera would bepreferred. However, due to considerations of expense, the continuousexposure camera has not yet become the one commonly in use. While theLand camera photographs 39 are usually used for navigation purposesonly, they may be used to supplement the larger views 4l if desired.

Various other cameras are the equivalents of the Land cameras. Certainof these operate on electrostatic principles, i. e. the Carlson processof "Xerogra-phy. One such equivalent camera is in use by the U. S. ArmySignal Corps and is by it known unoificially as Two Minute Minnie.

While only one Land camera is in use at one time, it is preferred tohave two such cameras available, one on each side of the fuselage. Theaircraft is then prepared to map in either leftto-right progression orright-to-left. Operation of both left and right cameras during astraight flight course, one photographing the center line of the nextflight course and the other photographing the apparent middle line ofthe preceding iiight course is of value. The photographs of thepreceding flight course can be compared with the Land photographs ofthat course when it was still to be mapped with the mapping camera. Ifthe two middle lines in both sets of Land photographs do not bear thesame relation to known landmarks then the aircraft must have drifted oifcourse.

What l claim is:

1. The method of aerial mapping of terrain from an aircraft whichcomprises flying parallel courses and turns connecting said courses,photographically recording the topography of the terrain directlybeneath the aircraft and simultaneously recording the topography of theterrain at an oblique angle to a line drawn from the aircraftperpendicular to the earths surface and substantially at a 45 angle inelevation from said perpendicular, developing the latent photographicimage of the oblique View while said aircraft is in flight, establishinga Well defined center line on the developed image parallel to the lineof flight, iiying said adjacent course along a line of the terrainrepresented substantially by the center line of the just-developed imageand repeating the recording op-eration in relation to the previouslyunrecorded strip of terrain toward which the aircraft has advanced.

2. A method of aerial mapping of terrain from an aircraft comprisingflying a course above an initial line of said terrain, simultaneouslyphotographing the terrain successively along said course from avertically stationed mapping camera in the aircraft and the terrainadjacent thereto in the direction of the terrain to be mapped from anobliquely directed sighting carnera, developing the successive latentphotographic images obtained from the sighting camera while proceedingon course, establishing a center line on the images so developed toprovide a line of flight to follow as the aircraft completes the initialcourse, and turning the aircraft to follow the line of iiight sodetermined and repeating the photographing proceeding along suchsucceeding line of night.

3. A method of aerial mapping from a moving aircraft which is iiying ina parallel grid pattern, the steps of which method comprisingphotographing simultaneously the terrain directly under the aircraftwith a mapping cameraJ and simultaneously the adjacent terrain to theside of the aircraft from an obliquely arranged sighting camera havingva Wire stretched in the focal plane thereof so as to divide the Viewstaken thereby centrally thereof, developing the views obtained by thesighting camera While the aircraft is on the straight flight mappingcourse,

with the sole exception of the last photograph,Y

developing said last photograph obtained from the obliquely sightedcamera While making the hairpin turn necessary to direct the aircraft toits succeeding flight mapping course, establishing the initial point onsuch succeeding course as determined by the line centrally of said lastphotograph, aligning the successively developed photographs taken in thestraight flight mapping course by the sighting camera in reverse order,selecting the succeeding flight mapping course from the photographs soaligned, flying such course and repeating the photographing procedure insuccessive order.

4. The process of aerial mapping from an aircraft which is moving in aparallel grid pattern over the terrain to be mapped, which processcomprises the steps of photographing the terrain directly underr theaircraft with a conventional mapping camera and the terrain in thedirection of the area to 'ne mapped to the side of the aircraftsuccessively with a Land type camera mounted substantially at a 45 angleto a vertical, developing the successive prints taken by the Land typecamera substantially immediately, aligning the prints as they aredeveloped While in ight, selecting the succeeding flight course from thealigned prints, executing a turn to direct the .aircraft to follow suchsucceeding flight course, and repeating the photographing procedurealong the so determined flight course.

5. Theprocess of mapping terrain from a moving aircraft which contains avertically mounted mapping camera and one or more Land cameras mountedat 90 to the longitudinal axis of the aircraft and substantially 45 fromthe perpendicular extending from the aircraft to the earths surface,said process comprising photographing simultaneously with all cameras atpredetermined uniform intervais obtaining views of substantially al1 the`terrain traversed and oblique Views of substantially all the terrain tobe traversed in the next flight path, developing the oblique views inight as they are obtained, aligning such views as they are obtained .andestablishing a center line thereon to serve as a flight path for thesucceeding flight course, and turning the aircraft into the flight pathso determined, repeating the photographing procedure, providing asubstantially uniform side lap of the photographs taken by the mappingcamera on succeeding flight courses.

JAWS E. HENRY.

References Cited in the le of this patent FOREIGN PATENTS Number CountryDate 441,235 Great Britain Jan. l5, 1936 OTHER REFERENCES McKinley,Applied Aerial Photography, Wiley-Sons, N. Y., 1929, pages 102-104.(Copy in Div. 7.)

McKinley, Applied Aerial Photography, Wiley-Sons, N. Y., 1929, pp.10-16. (Copy in Div. 7.)

